The manufacture of the 'o' ring tap since 1968, has seen improvements in style, of this high vacuum greasefree stopcock, with the discovery of a method of sealing an 'o' ring beneath a P.T.F.E.sheath, (figs 1 & 2), with no loss of performance and the added advantage of an unbreakable piston, we feel that the best valve has arrived, but knowing that the glass piston (fig. 3) with a combination of rings is so popular we are continuing to offer both pistons. Also the many and varied requirements of laboratory workers have made other seals desirable, therefore we supply the P.T.F.E.piston as standard, as this covers most applications but still offer glass pistons with combinations P.T.F.E.& viton 'o' rings, for those who still prefer it, and also a glass piston with elastomer rings for those who cannot tolerate P.T.F.E.for those, 'o' rings of viton a or silicon are available, but it must be the special elastomer piston as housings are of a different shape to contain elastomers.

Therefore all products listed in this catalogue will be supplied with P.T.F.E.pistons unless an alternative is requested. Recommended uses where glass pistons may be prefered for low temperature below - 50°C and very long term storage (i.e. over a year or more). If P.T.F.E., is attacked by your materials, e.g. with bromine or ozone, our glass piston with viton 'o' ring maybe preferred.


Our stopcocks are available with the choice of two types of threads (a). Fine thread (cat.no. POR) with sizes 1mm - 3mm bore with sidearms using capillary tubing, 4mm - 8mm, 10mm, 15mm, 20mm and 25mm bore with sidearms using standard tubing. (b). Fast thread (cat.no. PTT) with sizes 1mm - 3mm bore with sidearms using capillary tubing and 4mm - 8mm, 10mm with sidearms using standard tubing.

Developments over the last several years has seen the addition of needle valves, general purposes taps, air leak valves, nmr valves, vacuum-back valves, long neck taps and micro valves ranges available.

Under normal conditions thousands of hours use can be expected, as wear can only occur to the 'o' rings which are easily replaced. Cleaning is no longer a problem as all surfaces are glazed, therefore a grease free system is obtained needing the simplest maintenance.

Vacuums of 10-8 torr have been obtained by users, we will however guarantee 10-6 torr. The 'o' ring tap is also ideal under high pressure, and general chemical uses.